In a case with statewide significance, the Santa Clara County District Attorney's Office is pursuing a Sunnyvale couple under a little-known California law because redwood trees in their backyard cast a shadow over their neighbor's solar panels.

Richard Treanor and Carolynn Bissett own a Prius and consider themselves environmentalists. But they refuse to cut down any of the trees behind their house on Benton Street, saying they've done nothing wrong.

"We're just living here in peace. We want to be left alone," said Bissett, who with her husband has spent $25,000 defending themselves against criminal charges. "We support solar power, but we thought common sense would prevail."

Their neighbor Mark Vargas considers himself an environmentalist, too. His 10-kilowatt solar system, which he installed in 2001, is so big he pays only about $60 a year in electrical bills. He drives an electric car.

Vargas said he first asked Treanor and Bissett to chop down the eight redwoods, which the couple had planted from 1997 to 1999 along the fence separating their yards. Later, he asked them to trim the trees to about 15 feet.

"I offered to pay for the removal of the trees. I said let's try to work something out," Vargas said. "They said no to everything."

He installed the panels.

Complaint filed

After several years of squabbling and failed mediation, Vargas filed a complaint with the Santa Clara County district attorney arguing that the trees reduce the amount of electricity he can generate. In 2005, prosecutors agreed.

They sent Treanor and Bissett a letter informing them that they were in violation of California's Solar Shade Control Act and that if they didn't "abate the violation" within 30 days, they would face fines of up to $1,000 a day.

The law, signed by former Gov. Jerry Brown in 1978, is rarely used. But county prosecutors say Treanor and Bissett are breaking it.

"It's not that we think trees are more or less important than solar collectors. It's that our state's leaders have said under the following circumstances, solar takes precedence," said Ken Rosenblatt, supervising Santa Clara County deputy district attorney for environmental protection.

The law was written by former Assemblyman Chuck Imbrecht, a Ventura Republican, as a way to guarantee, amid the energy crises of the 1970s, that people who installed solar panels wouldn't see a drop in their investment from nearby trees.

It affects only trees planted after 1979, and bans trees or shrubs from shading more than 10 percent of a neighbor's solar panels between 10 a.m. and 2 p.m.

It does not apply to trees or shrubs that were there before the solar panels were installed. But — and here's the key distinction — it does apply to existing trees and shrubs that later grew big enough to shade the solar panels. A violation is an infraction, like a parking ticket, but with fines of up to $1,000 a day.

Setting a precedent?

The redwoods, which Treanor and Bissett say they planted for privacy, are now between 20 and 40 feet tall.

In December, Santa Clara County Superior Court Judge Kurt Kumli found the couple guilty of one count of violating the Solar Shade Control Act. In a partial victory for each side, he ruled that six of the trees can remain and that the two generating the most shade must be removed. He also waived any fines.

But the couple appealed. Why?

They are worried that their case sets a precedent.

Their lawyer can find no other conviction under the shade law.

"We could be done with this and walk away," Bissett said. "But then this could start happening in every city in the state."